The present invention relates to a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part and an electrophotographic photosensitive drum. Here, the electrophotographic image forming apparatus means an apparatus using an electrophotographic image formation type process to form an image on a recording medium. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (laser beam printer, LED printer or the like), a facsimile device and a word processor.
Here, the process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as a unit an electrophotographic photosensitive member and at least one one of process means such as charging means, developing means, cleaning means or the like. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as an unit a electrophotographic photosensitive member and a process means such as charging means, developing means, cleaning means or the like. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as a unit an electrophotographic photosensitive member and developing means. Since the process cartridge is detachably mountable relative to the main assembly of the device, the maintenance of the device is easy.
An electrophotographic image forming apparatus using the electrophotographic image formation type is such that a latent image is formed by selectively exposing the electrophotographic photosensitive member uniformly charged by charging means to image information light. The latent image is developed with toner by a developing means into a toner image. The toner image thus formed is transferred onto a recording medium by transferring means to form an image on the recording material.
Various methods have been proposed to rotate the electrophotographic photosensitive drum.
In one method, as disclosed U.S. Pat. No. 5,023,660, pins fixed on a side surface of the gear provided on the main assembly are engaged with recesses formed in a side surface of a gear provided in the photosensitive drum, by which the photosensitive drum is rotated.
In another method, as disclosed U.S. Pat. No. 4,829,335, a helical gear provided in the main assembly and the helical gear provided on the photosensitive drum, are engaged to rotate the photosensitive drum.
These methods are both very effective for transmitting the rotation force to the photosensitive drum. The present invention is a further and fundamental improvement of the conventional methods and structures.
Accordingly, it is a principal object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part, and an electrophotographic photosensitive drum, wherein rotation accuracy of the electrophotographic photosensitive drum is improved.
It is another object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part, and an electrophotographic photosensitive drum, wherein the driving force is transmitted to the electrophotographic photosensitive drum from the main assembly assuredly.
It is a further object of the present invention to provide a process cartridge, electrophotographic image forming apparatus, driving force transmission part, and an electrophotographic photosensitive drum, wherein the rotation center of a coupling of the main assembly of the device is made concentric with the rotation center of a coupling of the electrophotographic photosensitive drum when the driving force is transmitted (upon an image forming operation).
It is a further object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part and an electrophotographic photosensitive drum, wherein the positioning of the process cartridge relative to the device is improved by pulling the electrophotographic photosensitive drum into the main assembly side when the driving force is transmitted.
It is a further object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part, and an electrophotographic photosensitive drum, wherein an image quality is improved.
It is a further object of the present invention to provide a process cartridge, an electrophotographic image forming apparatus, a driving force transmission part, and an electrophotographic photosensitive drum, wherein the connection in the driving force transmission mechanism between the main assembly and the process cartridge is broken when the driving force is not transmitted (non-image-formation period), so that the operativity in demounting the process cartridge from the main assembly is improved.
According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an image forming apparatus for forming an image on a recording material, said main assembly including a motor, a driving rotatable member for receiving driving force from said motor and a twisted recess or projection having a non-circular cross-section and substantially coaxial with a rotation axis of said drive rotatable member, comprising: a rotatable image bearing member; process means actable on said photosensitive drum; and a twisted projection or recess provided at a longitudinal end of said image bearing member, having a non-circular cross-section and substantially coaxial with a rotation axis of said image bearing member, wherein said projection or recess of said image bearing member has such a dimension and configuration that it can take a first relative rotational position with respect to said recess or projection of said driving rotatable member in which relative rotational movement therebetween is permitted, and a second relative rotational position with respect to said recess or projection of said driving rotatable member in which relative rotational movement is prevented in one rotational direction, while the rotation axis of said driving rotatable member and the rotation axis of said image bearing member are substantially aligned.
According to another aspect of the present invention, there is provided an electrophotographic image forming apparatus for forming an image on a recording material, comprising: an electrophotographic photosensitive drum; charging means for charging said photosensitive drum; developing means for developing a latent image formed on said photosensitive drum into a toner image; transfer means for transferring the toner image onto the recording material; fixing means for fixing the toner image on the recording material; a motor; a main assembly side gear for receiving driving force from said motor; a twisted hole formed substantially at a center of said gear, said hole having a polygonal cross-section; a twisted prism projection provided at a longitudinal end of said photosensitive drum, wherein when said main assembly side gear rotates with said hole and projection engaged with each other, rotational driving force is transmitted from said gear to said photosensitive drum through said hole and said projection with said projection being pulled into said hole; and moving means for imparting relative movement between said hole and said projection in a longitudinal direction of said photosensitive drum.
According to another aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an image forming apparatus, wherein said main assembly includes a motor, a main assembly side gear for receiving driving force from said motor and a twisted hole formed substantially at a center of said gear, said hole having a polygonal cross-section; an electrophotographic photosensitive drum; process means actable on said photosensitive drum; and a twisted polygonal prism projection provided at a longitudinal end of said photosensitive drum, wherein when said main assembly side gear rotates with said hole and projection engaged with each other, rotational driving force is transmitted from said gear to said photosensitive drum through said hole and said projection with said projection being pulled into said hole.
According to another aspect of the present invention, there is provided an electrophotographic image forming apparatus, for forming an image on a recording material, to which a process cartridge is detachably mountable comprising: a motor; a main assembly side gear for receiving driving force from said motor; a twisted hole formed substantially at a center of said gear, said hole having a polygonal cross-section; means for mounting a process cartridge which includes: an electrophotographic photosensitive drum; process means actable on said photosensitive drum; a twisted polygonal prism projection provided at a longitudinal end of said photosensitive drum, wherein when said main assembly side gear rotates with said hole and projection engaged with each other, rotational driving force is transmitted from said gear to said photosensitive drum through said hole and said projection with said projection being pulled into said hole; and said apparatus further comprising; moving means for imparting relative movement between said hole and said projection in a longitudinal direction of said photosensitive drum; and means for feeding the recording material.
According to another aspect of the present invention, there is provided a drive transmission part for transmitting driving force to an electrophotographic photosensitive drum and a developing roller for developing a latent image formed on said photosensitive drum, which are contained in a process cartridge detachably mountable to a main assembly of an image forming apparatus for forming an image on a recording material, said main assembly including a motor, a main assembly side gear for receiving driving force from said motor, and a twisted hole formed substantially at a center of said gear, said hole having a polygonal cross-section; a gear for transmitting driving force to said developing roller from said main assembly to said developing roller when said process cartridge is mounted to the main assembly; and a shaft provided substantially at a center of said gear; and a twisted polygonal prism projection provided at an end of said shaft, wherein said projection receives driving force from the main assembly through engagement between said hole and projection, wherein the driving force is transmitted to said photosensitive drum through the shaft, and is transmitted to said developing roller through said gear.
According to another aspect of the present invention, there is provided a photosensitive drum, which is contained in a process cartridge detachably mountable to a main assembly of an image forming apparatus for forming an image on a recording material, said main assembly including a motor, a main assembly side gear for receiving driving force from said motor, and a twisted hole formed substantially at a center of said gear, said hole having a polygonal cross-section; a cylinder having a photosensitive layer thereon; a drive transmission member mounted to an end of said cylinder, said transmission member including: a gear for transmitting driving force to said developing roller from said main assembly to said developing roller when said process cartridge is mounted to the main assembly; a shaft provided substantially at a center of said gear; and a twisted polygonal prism projection provided at an end of said shaft, wherein said projection receives driving force from the main assembly through engagement between said hole and projection, wherein the driving force is transmitted to said photosensitive drum through the shaft, and is transmitted to said developing roller through said gear.
In the foregoing the recess and projection may be exchanged with each other.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.